U.S. patent application number 12/870429 was filed with the patent office on 2011-03-03 for apparatus and method for transceiving signals using frame structure in wireless communication system.
This patent application is currently assigned to LG Electronics Inc.. Invention is credited to Han Gyu Cho, Jin Sam Kwak, Dong Guk Lim, Sung Ho Moon.
Application Number | 20110051632 12/870429 |
Document ID | / |
Family ID | 43930930 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110051632 |
Kind Code |
A1 |
Lim; Dong Guk ; et
al. |
March 3, 2011 |
APPARATUS AND METHOD FOR TRANSCEIVING SIGNALS USING FRAME STRUCTURE
IN WIRELESS COMMUNICATION SYSTEM
Abstract
A method and apparatus for transceiving signals using a
predetermined frame structure in a wireless communication system is
provided. The apparatus includes a Radio Frequency (RF) unit for
transceiving a signal through a frame according to the
predetermined frame structure. The frame includes 5 subframes, the
5 subframe comprise type-1 subframes including 6 Orthogonal
Frequency Division Multiplex Access (OFDMA) symbols and type-2
subframes including 7 OFDMA symbols, and a Cyclic Prefix (CP)
length of the frame corresponds to 1/8 of an effective symbol
length.
Inventors: |
Lim; Dong Guk; (Anyang-si,
KR) ; Cho; Han Gyu; (Anyang-si, KR) ; Moon;
Sung Ho; (Anyang-si, KR) ; Kwak; Jin Sam;
(Gyeonggi-do, KR) |
Assignee: |
LG Electronics Inc.
Seoul
KR
|
Family ID: |
43930930 |
Appl. No.: |
12/870429 |
Filed: |
August 27, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61237304 |
Aug 27, 2009 |
|
|
|
Current U.S.
Class: |
370/280 ;
370/344 |
Current CPC
Class: |
H04L 27/2604 20130101;
H04L 27/2602 20130101; H04L 27/2607 20130101 |
Class at
Publication: |
370/280 ;
370/344 |
International
Class: |
H04B 7/208 20060101
H04B007/208; H04J 3/00 20060101 H04J003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2010 |
KR |
10-2010-0064890 |
Claims
1. A method for transceiving signals using a predetermined frame
structure in a wireless communication system, the method
comprising: transceiving a signal through a frame according to the
predetermined frame structure, wherein the frame includes 5
subframes, the 5 subframes comprise type-1 subframes including 6
Orthogonal Frequency Division Multiplex Access (OFDMA) symbols and
type-2 subframes including 7 OFDMA symbols, wherein a Cyclic Prefix
(CP) length of the frame corresponds to 1/8 of an effective symbol
length.
2. The method according to claim 1, wherein the frame is a Time
Division Duplex (TDD) frame or a Frequency Division Duplex (FDD)
frame.
3. The method according to claim 2, wherein the frame is a TDD
frame and the TDD frame includes 2 type-1 subframes and 3 type-2
subframes.
4. The method according to claim 3, wherein the TDD frame includes
a downlink interval and an uplink interval subsequent to the
downlink interval and a Transmit Transition Gap (TTG) interval is
located between the downlink interval and the uplink interval and a
Receive Transition Gap (RTG) interval is located next to a last
subframe of the uplink interval.
5. The method according to claim 3, wherein a ratio of a number of
downlink subframes to a number of uplink subframes in the TDD frame
is 3:2 or 2:3.
6. The method according to claim 3, wherein a symbol allocated to
the TTG or RTG interval is located at a first symbol of a first
uplink subframe of the TDD frame.
7. The method according to claim 6, wherein the first uplink
subframe of the TDD frame is a type-1 subframe.
8. The method according to claim 2, wherein the frame has a channel
bandwidth of 7 MHz.
9. The method according to claim 2, wherein the TDD frame includes
33 OFDMA symbols and the FDD frame includes 34 OFDMA symbols.
10. An apparatus for transceiving signals using a predetermined
frame structure in a wireless communication system, the apparatus
comprising: a Radio Frequency (RF) unit for transceiving a signal
through a frame according to the predetermined frame structure,
wherein the frame includes 5 subframes, the 5 subframes comprise
type-1 subframes including 6 Orthogonal Frequency Division
Multiplex Access (OFDMA) symbols and type-2 subframes including 7
OFDMA symbols, wherein a Cyclic Prefix (CP) length of the frame
corresponds to 1/8 of an effective symbol length.
11. The apparatus according to claim 10, wherein the frame is a
Time Division Duplex (TDD) frame or a Frequency Division Duplex
(FDD) frame.
12. The apparatus according to claim 11, wherein the frame is a TDD
frame and the TDD frame includes 2 type-1 subframes and 3 type-2
subframes.
13. The apparatus according to claim 12, wherein the TDD frame
includes a downlink interval and an uplink interval subsequent to
the downlink interval and a Transmit Transition Gap (TTG) interval
is located between the downlink section and the uplink interval and
a Receive Transition Gap (RTG) interval is located next to a last
subframe of the uplink interval.
14. The apparatus according to claim 12, wherein a ratio of a
number of downlink subframes to a number of uplink subframes in the
TDD frame is 3:2 or 2:3.
15. The apparatus according to claim 12, wherein a symbol allocated
to the TTG or RTG interval is located at a first symbol of a first
uplink subframe of the TDD frame.
16. The apparatus according to claim 15, wherein the first uplink
subframe of the TDD frame is a type-1 subframe.
17. The apparatus according to claim 11, wherein the frame has a
channel bandwidth of 7 MHz.
18. The apparatus according to claim 11, wherein the TDD frame
includes 33 OFDMA symbols and the FDD frame includes 34 OFDMA
symbols.
Description
[0001] Pursuant to 35 U.S.C. .sctn.119(e), this application claims
the benefit of priority to Provisional Application No. 61/237,304,
filed on Aug. 27, 2009.
[0002] Pursuant to 35 U.S.C. .sctn.119(e), this application claims
the benefit of priority to Korean application No. 10-2010-0064890,
filed on Jul. 6, 2010.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to a wireless communication
system, and more particularly, to an apparatus and method for
transmitting and receiving signals using a frame structure in a
wireless communication system.
[0005] 2. Discussion of the Related Art
[0006] An Institute of Electrical and Electronics Engineers (IEEE)
802.16m system supports both a Frequency Division Duplex (FDD)
scheme, including a Half-Frequency Division Duplex (H-FDD) Mobile
Station (MS) operation scheme, and a Time Division Duplex (TDD)
scheme.
[0007] The 802.16m system uses an Orthogonal Frequency Division
Multiplex Access (OFDMA) scheme as a multiple access scheme in
downlink and uplink.
[0008] The following is a brief description of a frame structure of
an IEEE 802.16m system which is an exemplary mobile communication
system.
[0009] FIG. 1 illustrates a basic frame structure in an IEEE
802.16m system.
[0010] As shown in FIG. 1, each 20 ms superframe is divided into
four 5 ms radio frames having the same size and starts at a
SuperFrame Header (SFH). When one of the channel bandwidths of 5
MHz, 10 MHz, and 20 MHz is used, each 5 ms radio frame includes 8
subframes. One subframe may be allocated for downlink or uplink
transmission.
[0011] The IEEE 802.16m system, which is an exemplary mobile
communication system, uses three or more types of subframes. A
type-1 subframe includes 6 OFDMA symbols, a type-2 subframe
includes 7 OFDMA symbols, a type-3 subframe includes 5 OFDMA
symbols.
[0012] The basic frame structure is applicable to both the FDD
scheme, including the H-FDD MS operation scheme, and the TDD
scheme. The number of switching points in each radio frame in the
TDD system is 2. The switching points may be defined according to
directionality changes from downlink to uplink or from uplink to
downlink.
[0013] The H-FDD Mobile Station (MS) may be included in an FDD
system, and a frame structure for the H-FDD MS is similar to a TDD
frame structure. However, in the FDD system, downlink and uplink
transmission are performed in two separate frequency bands.
Transmission and reception circuits need to be switched in
transmission gaps between downlink and uplink transmissions and
between downlink and uplink transmissions.
[0014] Frame structures having a CP length corresponding to 1/8 of
an effective symbol length Tb for a channel bandwidth of 7 MHz,
other than the basic frame structure of the IEEE 802.16m system,
have yet to be suggested.
SUMMARY OF THE INVENTION
[0015] An object of the present invention devised to solve the
problem lies on an apparatus for transmitting and receiving signals
using a frame structure in a wireless communication system.
[0016] Another object of the present invention devised to solve the
problem lies on a method for transmitting and receiving signals
using a frame structure in a wireless communication system.
[0017] Objects of the present invention are not limited to those
described above and other objects will be clearly understood by
those skilled in the art from the following description.
[0018] The object of the present invention can be achieved by
providing an apparatus for transceiving signals using a
predetermined frame structure in a wireless communication system,
the apparatus including a Radio Frequency (RF) unit for
transceiving a signal through a frame according to the
predetermined frame structure, wherein the frame includes 5
subframes, the 5 subframes comprise type-1 subframes including 6
Orthogonal Frequency Division Multiplex Access (OFDMA) symbols and
type-2 subframes including 7 OFDMA symbols, wherein a Cyclic Prefix
(CP) length of the frame corresponds to 1/8 of an effective symbol
length.
[0019] The frame may be a Time Division Duplex (TDD) frame or a
Frequency Division Duplex (FDD) frame.
[0020] The TDD frame may include 2 type-1 subframes and 3 type-2
subframes.
[0021] The TDD frame may include a downlink interval and an uplink
interval subsequent to the downlink interval and a Transmit
Transition Gap (TTG) interval may be located between the downlink
interval and the uplink interval and a Receive Transition Gap (RTG)
interval may be located subsequent to a last subframe of the uplink
interval.
[0022] A ratio of a number of downlink subframes to a number of
uplink subframes in the TDD frame may be 3:2 or 2:3.
[0023] The TDD frame may include 2 type-1 subframes and 3 type-2
subframes.
[0024] Preferably, a symbol allocated to the TTG or RTG interval is
located at a first symbol of a first uplink subframe of the TDD
frame. Here, the first uplink subframe of the TDD frame may have 7
symbols, but one symbol of the first uplink subframe of the TDD
frame is allocated to a transition gap. Therefore, the first uplink
subframe of the TDD frame Type-1 subframe including 6 symbols.
[0025] The frame may have a channel bandwidth of 7 MHz and the TDD
frame may include 33 OFDMA symbols and the FDD frame may include 34
OFDMA symbols.
[0026] In another aspect of the present invention, provided herein
is a method for transmitting and receiving signals using a
predetermined frame structure in a wireless communication system,
the method including transceiving a signal through a frame
according to the predetermined frame structure, wherein the frame
includes subframes, the 5 subframes comprise type-1 subframes
including 6 Orthogonal Frequency Division Multiplex Access (OFDMA)
symbols and type-2 subframes including 7 OFDMA symbols, wherein a
Cyclic Prefix (CP) length of the frame corresponds to 1/8 of an
effective symbol length.
[0027] The frame may be a Time Division Duplex (TDD) frame or a
Frequency Division Duplex (FDD) frame.
[0028] The TDD frame may include 2 type-1 subframes and 3 type-2
subframes.
[0029] The TDD frame may include a downlink interval and an uplink
interval subsequent to the downlink interval and a Transmit
Transition Gap (TTG) interval may be located between the downlink
interval and the uplink interval and a Receive Transition Gap (RTG)
interval may be located next to a last subframe of the uplink
interval.
[0030] A ratio of a number of downlink subframes to a number of
uplink subframes in the TDD frame may be 3:2 or 2:3.
[0031] Preferably, a symbol allocated to the TTG or RTG interval is
located at a first symbol of a first uplink subframe of the TDD
frame. Here, the first uplink subframe of the TDD frame may have 7
symbols, but one symbol of the first uplink subframe of the TDD
frame is allocated to a transition gap. Therefore, the first uplink
subframe of the TDD frame Type-1 subframe including 6 symbols.
[0032] The frame may have a channel bandwidth of 7 MHz and the TDD
frame may include 33 OFDMA symbols and the FDD frame may include 34
OFDMA symbols.
[0033] According to the present invention, it is possible to
efficiently transmit and receive signals using a frame structure
having a CP length corresponding to 1/8 of an effective symbol
length for a channel bandwidth of 7 MHz.
[0034] In addition, it is possible to efficiently transmit and
receive signals using a frame structure, which has a CP length
corresponding to 1/8 of an effective symbol length and which is
designed to coexist with frame structures having other CP lengths
according to the present invention, without causing collision and
interference with frame structures having other CP lengths.
[0035] Advantages of the present invention are not limited to those
described above and other advantages will be clearly understood by
those skilled in the art from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The accompanying drawings, which are included to provide a
further understanding of the invention, illustrate embodiments of
the invention and together with the description serve to explain
the principle of the invention.
[0037] In the drawings:
[0038] FIG. 1 illustrates a basic frame structure in an IEEE
802.16m system.
[0039] FIG. 2 illustrates an example of a symbol structure
including a Cyclic Prefix (CP).
[0040] FIG. 3 illustrates an exemplary TDD frame structure which
has a CP length corresponding to 1/8 of the effective symbol length
Tb for a channel bandwidth of 7 MHz in an IEEE 802.16m system which
is an exemplary mobile communication system.
[0041] FIG. 4 illustrates an exemplary FDD frame structure which
has a CP length corresponding to 1/8 of the effective symbol length
Tb for a channel bandwidth of 7 MHz in an IEEE 802.16m system which
is an exemplary mobile communication system.
[0042] FIG. 5 illustrates exemplary frame structures of the IEEE
802.16m system having a CP length of 1/8 Tb for a channel bandwidth
of 7 MHz according to the present invention.
[0043] FIG. 6 illustrates an exemplary TDD frame structure that
supports a legacy mode.
[0044] FIG. 7 is a block diagram illustrating components of a
signal transceiver according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0045] Reference will now be made in detail to the preferred
embodiments of the present invention with reference to the
accompanying drawings. The detailed description, which will be
given below with reference to the accompanying drawings, is
intended to explain exemplary embodiments of the present invention,
rather than to show the only embodiments that can be implemented
according to the invention. The following detailed description
includes specific details in order to provide a thorough
understanding of the present invention. However, it will be
apparent to those skilled in the art that the present invention may
be practiced without such specific details. For example, although
the following descriptions will be given in detail with reference
to the case where the mobile communication system is a 3rd
Generation Partnership Project Long Term Evolution (3GPP LTE)
system, the following descriptions, except those specific to 3GPP
LTE, may be applied to any other mobile communication system.
[0046] In some instances, known structures and devices are omitted
or shown in block diagram form, focusing on important features of
the structures and devices, so as not to obscure the concept of the
present invention. The same reference numbers will be used
throughout this specification to refer to the same or like
parts.
[0047] In the following description, the term "Mobile Station (MS)"
is used to generally describe any mobile or stationary user device
such as a User Equipment (UE) or an Advance Mobile Station (AMS).
In addition, the term "Base Station (BS)" is used to generally
describe any network node that communicates with the MS such as a
Node B, an eNode B, or an Access Point (AP).
[0048] In a mobile communication system, an MS may receive
information from a BS in downlink and may transmit information to
the BS in uplink. Information transmitted or received by the MS
includes data and various control information. Various physical
channels are provided according to types and purposes of
information transmitted or received by the MS.
[0049] In the 3GPP LTE system, which is an example of the mobile
communication system, Orthogonal Frequency Division Multiplexing
(OFDM) is used as a multicarrier modulation scheme. The following
is a brief description of the basic principle of the OFDM
scheme.
[0050] In the OFDM system, a high rate data stream is divided into
a large number of low rate data streams to simultaneously transmit
the low rate data streams using a plurality of carriers. Each of
the plurality of carriers is referred to as a "subcarrier". Since
orthogonality exists between the subcarriers in the OFDM system, it
is possible for a receiving side to detect the subcarriers even
when frequency components of the subcarriers overlap each other. A
high rate data stream may be converted into a plurality of parallel
low rate data streams through a serial-to-parallel converter and
the parallel low rate data streams may be multiplied by respective
subcarriers and then combined and transmitted to the receiving
side.
[0051] The parallel data streams generated by the
serial-to-parallel converter may be transmitted through a plurality
of subcarriers using an Inverse Discrete Fourier Transform (IDFT).
The IDFT may be efficiently implemented using an Inverse Fast
Fourier Transform (IFFT). The relative signal dispersion of each of
the low rate subcarriers in the time domain, which is caused by
multipath delay spread, is decreased since the symbol duration of
each low rate subcarrier is increased.
[0052] A guard interval longer than the channel delay spread may be
inserted between OFDM symbols to reduce Inter-symbol interference
in wireless communication using the OFDM scheme. Specifically, a
guard interval longer than the maximum channel delay spread is
inserted between consecutive symbols while each symbol is
transmitted through multipath channels. Here, a signal in a last
part (i.e., in a guard interval) of the effective symbol duration
of a symbol is copied and inserted at the beginning of the symbol
to prevent loss of orthogonality between subcarriers. This inserted
portion is referred to as a "Cyclic Prefix (CP).
[0053] FIG. 2 illustrates an example of a symbol structure
including a Cyclic Prefix (CP).
[0054] Referring to FIG. 2, a symbol period Ts is the sum of a
guard interval Tg and an effective symbol duration Tb for carrying
data. The receiving side demodulates a symbol by removing a guard
interval Tg of the symbol and extracting data from an effective
symbol duration thereof. The transmitting side and the receiving
side can achieve synchronization and maintain orthogonality between
data symbols using a CP code. The term "symbol" as used in the
present invention may refer to an OFDMA symbol.
[0055] FIG. 3 illustrates an exemplary TDD frame structure which
has a CP length corresponding to 1/8 of the effective symbol length
Tb for a channel bandwidth of 7 MHz in an IEEE 802.16m system which
is an exemplary mobile communication system.
[0056] As shown in FIG. 3, in the exemplary TDD frame structure, a
ratio of the number of downlink subframes to the number of uplink
subframes in one frame may be 4:2. The TDD frame may have a channel
bandwidth of 7 MHz and may have a CP length corresponding to 1/8 of
the effective symbol length Tb.
[0057] Among 6 subframes included in one frame, 3 subframes may be
type-1 subframes, each including 6 symbols, and the 3 remaining
subframes may be type-3 subframes, each including 5 symbols. Here,
the second, third, and fourth subframes which are arranged in
temporal order in one frame may be type-3 subframes.
[0058] As can be seen from FIG. 3, the length of a Transmit
Transition Gap (TTG) located at the time of downlink to uplink
transition may be 188 .mu.s and the length of a Receive Transition
Gap (RTG) located at the time of uplink to downlink transition may
be 60 .mu.s.
[0059] FIG. 4 illustrates an exemplary FDD frame structure which
has a CP length corresponding to 1/8 of the effective symbol length
Tb for a channel bandwidth of 7 MHz in an IEEE 802.16m system which
is an exemplary mobile communication system.
[0060] As shown in FIG. 4, in the exemplary FDD frame structure,
the FDD frame may have a channel bandwidth of 7 MHz and may have a
CP length corresponding to 1/8 of the effective symbol length
Tb.
[0061] Among 6 subframes included in one frame, 4 subframes may be
type-1 subframes, each including 6 symbols, and the 2 remaining
subframes may be type-3 subframes, each including 5 symbols. Here,
the second, third, and fourth subframes which are arranged in
temporal order in one frame may be type-3 subframes.
[0062] As described above, each of the TDD and FDD frame structures
shown respectively in FIGS. 3 and 4, which has a CP length
corresponding to 1/8 of the effective symbol length Tb for a
channel bandwidth of 7 MHz, may include type-1 subframes, each
including 6 symbols, and type-3 subframes, each including 5
symbols. Accordingly, the frame structure, which has a CP length
corresponding to 1/8 of the effective symbol length Tb for a
channel bandwidth of 7 MHz as shown in FIGS. 3 and 4, requires a
new type of uplink control channel including 5 symbols in the
uplink region since the frame structure includes type-3 subframes.
However, it is difficult to smoothly transmit control information
using the frame structure shown in FIGS. 3 and 4 since the current
control channel consists of type-1 subframes alone.
[0063] The following Table 1 illustrates OFDMA parameters applied
to the IEEE 802.16m system which is an exemplary mobile
communication system.
TABLE-US-00001 TABLE 1 The nominal channel bandwidth, BW (MHz) 5 7
8.75 10 20 Sampling factor, n 28/25 8/7 8/7 28/25 28/25 Sampling
frequency, F.sub.s (MHz) 5.6 8 10 11.2 22.4 FFT size, N.sub.FFT 512
1024 1024 1024 2048 Subcarrier spacing, .DELTA.f (kHz) 10.94 7.81
9.77 10.94 10.94 Useful symbol time, T.sub.b (.mu.s) 91.4 128 102.4
91.4 91.4 CP ratio, G = 1/8 OFDMA symbol time, T.sub.s (.mu.s)
102.857 144 115.2 102.857 102.857 FDD Number of 48 34 43 48 48
OFDMA symbols per 5 ms frame TDD Idle time (.mu.s) 62.857 104 46.40
62.857 62.857 Number of 47 33 42 47 47 OFDMA symbols per 5 ms frame
TTG + RTG (.mu.s) 165.714 248 161.6 165.714 165.714 CP ratio, G =
1/16 OFDMA symbol time, T.sub.s (.mu.s) 97.143 136 108.8 97.143
97.143 FDD Number of 51 36 45 51 51 OFDMA symbols per 5 ms frame
TDD Idle time (.mu.s) 45.71 104 104 45.71 45.71 Number of 50 35 44
50 50 OFDMA symbols per 5 ms frame TTG + RTG (.mu.s) 142.853 240
212.8 142.853 142.853 CP ratio, G = 1/4 OFDMA symbol time, T.sub.s
(.mu.s) 114.286 160 128 114.286 114.286 FDD Number of 43 31 39 43
43 OFDMA symbols per 5 ms frame Idle time (.mu.s) 85.694 40 8
85.694 85.694 TDD Number of 42 30 37 42 42 OFDMA symbols per 5 ms
frame TTG + RTG (.mu.s) 199.98 200 264 199.98 199.98
[0064] The following Table 2 illustrates additional OFDMA
parameters other than those of Table 1.
TABLE-US-00002 TABLE 2 The nominal channel bandwidth, BW (MHz) 5 7
8.75 10 20 Number of guard Left 40 80 80 80 160 sub-carriers Right
39 79 79 79 159 Number of used sub-carriers 433 865 865 865 1729
Number of physical resource 24 48 48 48 96 unit (18 .times. 6) in a
type-1 AAI subframe.
[0065] Frame structures (TDD and FDD frame structures) in the IEEE
802.16m system, each of which has a CP length corresponding to 1/8
of the effective symbol length Tb (i.e., a CP length of 1/8 Tb) for
a channel bandwidth of 7 MHz in an IEEE 802.16m system which is an
exemplary mobile communication system, are described below.
[0066] In addition, TDD frame structures suggested in the present
invention, which may coexist with TDD frame structures having a CP
length of 1/8 Tb or a CP length of 1/16 Tb for the same channel
bandwidth of 7 MHz, are described below. FDD frame structures that
have a number of features in common with the TDD frame structures
suggested in the present invention are also described below.
[0067] The TDD and FDD frame structures of the IEEE 802.16m system
having a CP length of 1/8 Tb for the 7 MHz channel bandwidth
suggested in the present invention have the OFDMA parameters
defined in the above Tables 1 and 2. The frame structures of the
IEEE 802.16m system having a CP length of 1/8 Tb for the 7 MHz
channel bandwidth suggested in the present invention have features
in common with the basic frame structures and may coexist with
frame structures having other CP lengths (for example, a CP length
of 1/16 Tb for the 7 MHz channel bandwidth). The frame structures
of the IEEE 802.16m system having a CP length of 1/8 Tb for the 7
MHz channel bandwidth suggested in the present invention may be
constructed such that their boundaries (or transition points)
between uplink and downlink do not overlap those of frame
structures having other CP lengths. Accordingly, the frame
structures of the IEEE 802.16m system having a CP length of 1/8 Tb
for the 7 MHz channel bandwidth suggested in the present invention
do not interfere with frame structures having other CP lengths and
therefore may coexist with frame structures having other CP
lengths.
[0068] FIG. 5 illustrates exemplary frame structures of the IEEE
802.16m system having a CP length of 1/8 Tb for a channel bandwidth
of 7 MHz according to the present invention.
[0069] TDD and FDD frame structures shown in FIGS. 5(a) to (c) use
OFDMA parameters shown in Tables 1 and 2. As shown in Tables 1 and
2, OFDMA parameters "symbol duration", "TTG", and "RTG" defined
when frame structure with a CP length of 1/8 Tb is used for the 7
MHz channel bandwidth are 144 .mu.s, 188 .mu.s, and 60 .mu.s,
respectively.
[0070] FIGS. 5(a) and (b) illustrate TDD frame structures of the
IEEE 802.16m system having a CP length of 1/8 Tb for the 7 MHz
channel bandwidth. As shown in FIGS. 5(a) and (b), a ratio of the
number of downlink subframes to the number of uplink subframes in a
TDD frame including 5 subframes may be 2:3 or 3:2.
[0071] As shown in FIGS. 5(a) and (b), a TDD frame may be
constructed of subframes including type-1 subframes, each including
6 OFDMA symbols, and type-2 subframes, each including 7 OFDMA
symbols, so as not to create a control channel constructed 5 OFDMA
symbols in the uplink region.
[0072] Taking into consideration the defined OFDMA parameters, it
can be seen that the number of OFDMA symbols included in one FDD
frame when a CP length of 1/8 Tb is used in the FDD frame is 34.
However, a TDD frame having a CP length of 1/8 Tb for a channel
bandwidth of 7 MHz according to the present invention requires
TTG/RTG intervals for switching between downlink and uplink.
Accordingly, one symbol may be allocated to the TTG/RTG. The number
of symbols of a TDD frame is 33, which is one less than the number
of symbols of an FDD frame, since one symbol is allocated to the
TTG/RTG in the TDD frame.
[0073] One TDD frame may include 5 subframes. Specifically, one TDD
frame may include 2 type-1 subframes and 3 type-2 subframes.
TTG/RTG intervals may be allocated to the first uplink subframe in
the TDD frame. To accomplish this, a type-2 subframe may be located
at the first uplink subframe position. One symbol allocated to the
TTG/RTG intervals is located at the first symbol position of the
first uplink subframe. The first uplink subframe has substantially
the same format as the type-1 subframe structure since one symbol
of the type-2 subframe at the first uplink subframe position is
allocated to TTG/RTG intervals.
[0074] As shown in FIGS. 5(a) and (b), type-1 subframes may be
located only at the first downlink subframe position and the first
uplink subframe position in a TDD frame. The number of symbols
allocated to downlink and the number of symbols allocated to uplink
in the TDD frame structure may be expressed by 6+7*(M-1), where M
is the number of subframes allocated to downlink, and 6+7*(N-1),
where N is the number of subframes allocated to uplink,
respectively.
[0075] As shown in the FDD frame of FIG. 5(c), the number of
symbols in the FDD frame is 34 since the FDD frame does not require
the TTG/RTG. The FDD frame may be constructed of type-1 subframes,
each including 6 OFDMA symbols, and type-2 subframes, each
including 7 OFDMA symbols, from among basic subframes, so as not to
create an uplink control channel constructed 5 OFDMA symbols in the
uplink region. In this case, one FDD frame includes 5
subframes.
[0076] One FDD frame having a CP length of 1/8 Tb for a channel
bandwidth of 7 MHz according to the present invention may be
constructed of 34 OFDMA symbols and may be constructed of 5
subframes. One FDD frame may also be constructed of one type-1
subframe and four type-2 subframes. Here, one type-1 subframe may
be located in the FDD frame at the subframe position that is first
in temporal order.
[0077] FIG. 6 illustrates an exemplary TDD frame structure that
supports a legacy mode.
[0078] A legacy system is a conventional system that complies with
conventional standards. The IEEE 802.16e system is one example of a
legacy system. However, the legacy system is not limited to the
IEEE 802.16e system. A new system which has evolved from the
conventional system may be installed in an area where the legacy
system is installed. In this case, the new system needs to support
not only the legacy MS but also new MSs. FIG. 6 illustrates a TDD
frame structure defined to support the legacy mode in the IEEE
802.16m system.
[0079] As shown in FIG. 6(a), 12 symbols need to be allocated to
the uplink region in order to support the legacy system. In
addition, an interval for downlink to uplink transition needs to be
located at the first uplink subframe. That is, a TTG may be located
at the first uplink subframe.
[0080] As shown in FIG. 6(a), the first uplink subframe may be
considered a type-2 subframe since the first uplink subframe
includes a total of 7 OFDMA symbols including an idle interval.
However, the first uplink subframe may substantially be assumed to
be a type-1 subframe including 6 symbols since one symbol of the
first uplink subframe is reserved to create a transition interval
(or a delay interval) required for the TTG in the TDD frame. That
is, by allocating an idle interval for the TTG in the uplink
region, the frame structure shown in FIG. 6(a) can sufficiently
support the legacy system and can also coexist with frame
structures having other CP lengths for the same channel bandwidth
as shown in FIG. 6(b) without interference therebetween. The frame
structure suggested so as not only to support the legacy system but
also to coexist with frame structures having other CP lengths as
described above can be applied, regardless of the ratio between the
number of downlink subframes and the number of uplink
subframes.
[0081] As described above, a TDD frame structure shown in FIG. 6(a)
can coexist with legacy-mode frame structures having other CP
lengths for the same channel bandwidth (for example, 7 MHz) without
interference therebetween.
[0082] In summary, using the frame structures shown in FIGS. 5 and
6, a signal transceiver (i.e., an MS or a BS) can efficiently
transmit and receive signals and can also efficiently transmit and
receive signals to and from a signal transceiver, which uses other
CP lengths, without interference and collision therebetween.
[0083] FIG. 7 is a block diagram illustrating components of a
signal transciever 50 according to the present invention.
[0084] As shown in FIG. 7, the signal transciever 50 may be an MS
or a BS. The signal transciever 50 includes a processor 51, a
memory 52, a Radio Frequency (RF) unit 53, a display unit 54, and a
user interface unit 55.
[0085] Layers of a radio interface protocol are implemented in the
processor 51. The processor 51 provides a control plane and a user
plane. Functions of the layers may be implemented in the processor
51. The memory 52 is connected to the processor 51 to store an
operating system, applications, and general files.
[0086] The display unit 54 displays a variety of information and
may include a well known element such as a Liquid Crystal Display
(LCD) or an Organic Light Emitting Diode (OLED).
[0087] The user interface unit 55 may include a combination of well
known user interfaces such as a keypad and a touch screen.
[0088] The RF unit 53 may be connected to the processor 51 to
transmit and receive radio signals. The RF unit 53 may be divided
into a transmission module (not shown) and a reception module (not
shown).
[0089] The layers of the radio interface protocol between an MS and
a network can be classified into a first layer L1, a second layer
L2 and a third layer L3 based on the three lower layers of an Open
System Interconnection (OSI) reference model widely known in the
field of communications. A physical layer belonging to the first
layer L1 provides an information transfer service using a physical
channel. A Radio Resource Control (RRC) layer located at the third
layer provides radio resources for control between the MS and the
network. The MS and the network exchange RRC messages through the
RRC layer.
[0090] Various embodiments have been described in the best mode for
carrying out the invention.
[0091] The above embodiments are provided by combining components
and features of the present invention in specific forms. The
components or features of the present invention should be
considered optional unless explicitly stated otherwise. The
components or features may be implemented without being combined
with other components or features. The embodiments of the present
invention may also be provided by combining some of the components
and/or features. The order of the operations described above in the
embodiments of the present invention may be changed. Some
components or features of one embodiment may be included in another
embodiment or may be replaced with corresponding components or
features of another embodiment. It will be apparent that claims
which are not explicitly dependent on each other can be combined to
provide an embodiment or new claims can be added through amendment
after this application is filed.
[0092] The embodiments of the present invention can be implemented
by hardware, firmware, software, or any combination thereof. In the
case where the present invention is implemented by hardware, the
method for transmitting and receiving signals using a predetermined
frame structure according to the embodiments of the present
invention may be implemented by one or more application specific
integrated circuits (ASICs), digital signal processors (DSPs),
digital signal processing devices (DSPDs), programmable logic
devices (PLDs), field programmable gate arrays (FPGAs), processors,
controllers, microcontrollers, microprocessors, or the like.
[0093] In the case where the present invention is implemented by
firmware or software, the embodiments of the present invention may
be implemented in the form of modules, processes, functions, or the
like which perform the features or operations described above.
Software code can be stored in a memory unit so as to be executed
by a processor. The memory unit may be located inside or outside
the processor and can communicate data with the processor through a
variety of known means.
[0094] Those skilled in the art will appreciate that the present
invention may be embodied in other specific forms than those set
forth herein without departing from the spirit and essential
characteristics of the present invention. The above description is
therefore to be construed in all aspects as illustrative and not
restrictive. The scope of the invention should be determined by
reasonable interpretation of the appended claims and all changes
coming within the equivalency range of the invention are intended
to be embraced in the scope of the invention.
* * * * *